Facsimile machines for business use or domestic use are generally equipped with automatic paper feed devices.
An automatic paper feed device, as is known to all interested, is designed to feed a number of sheets of documents sheet by sheet automatically, without the help of an operator, to the image-reading means.
Illustrating an automatic paper feed device in the prior art in a drawing in a later section, FIG. 8 shows an example of a conventional automatic paper feed device 30 which is equipped with a pad pressure adjusting mechanism 40.
As shown in FIG. 8, this device 30 has document feed rollers 4 consisting of a plurality of axially arranged roller elements (not illustrated in the drawing). Close to these rollers 4 is placed a guide plate 32 slanted at a certain angle, which controls the direction in which the sheets of documents 19, which are placed on the platen (not shown in the drawing), are forwarded therefrom. The numeral 33 in the drawing indicates a cutout which is opened as shown in the drawing at each of the areas where said document feed rollers 4 are provided.
Said pad pressure adjusting mechanism 40 is provided against the document feed rollers 4 with part of it in slidable contact with the treads of the rollers 4. A pad pressure adjusting means thereof, as is known, consists of a leaf spring 41 of a certain shape, a separating pad 42 attached by adhesion to the underside thereof, and a coil spring 46 provided, as shown in the drawing, between the leaf spring 41 and the main body 45 with said coil spring so designed as to press the separating pad 42 slidably against the treads of said rollers 4 with a set pressure. With such a mechanism, the pad pressure acting upon the document feed rollers 4 is maintained constant at all times.
The leaf spring 41, to which the separating pad 42 is attached, is fixed to a holding member 43 in the main body with a screw 44.
In an automatic paper feed device 30 set up as above, a number of sheets of documents 19 are laid in a layer on the guide plate 32, as shown in the drawing, when the document feed rollers 4 operate, one of the sheets is forwarded at a time by the separating action of the separating pad 42 and each sheet 19 is separately discharged in the direction shown by an arrow in the drawing. Each sheet of documents thus discharged is passed through an image-reading means (not shown in the drawing) whereby the contents (image) on the sheet are photoelectrically read.
Thus in a conventional automatic paper feed device 30 the separating pad 42 and the coil spring 46 jointly enable the document feed rollers 4 to pick each sheet from a number of sheets of documents 19 laid together on the guide plate 32 and send them sheet by sheet downward. The coil spring 46 is designed to maintain the pad pressure uniform at all times.
In such a pad pressure adjusting mechanism 40 based on a coil spring 46 for uniformity of pressure, however, the pad pressure cannot be adjusted to suit variable conditions. The operation, therefore, involves the possibility of not picking a sheet properly depending on the thickness, quality, and the like of the paper 19 used. For example, when the paper 19 used is thinner than in ordinary cases or is lacking in stiffness, a slight increase in pad pressure over the ordinary pressure serves to avoid picking two or more sheets 19 in overlap.
The conventional mechanism 40, furthermore, poses a problem that both the separating pad 42 and the document feed rollers 4 wear through the use over a long period, the pad pressure thus becoming inadequate while they are used for a long time.
Taking the above-mentioned problems into consideration, it is proposed, in accordance with this invention to introduce an automatic paper feed device having a pad pressure adjusting means which enables an operator to adjust the pad pressure according to the thickness, quality, or the like of the paper 19 used relatively easily from the outside of the apparatus.